1. Field of the Invention
The present invention relates to a gas distribution plate for use in a gas distribution assembly in a processing chamber, and to methods of fabricating the gas distribution plate.
2. Description of the Background Art
Corrosion (including erosion) resistance is a critical property for apparatus components used in processing chambers where corrosive environments are present, such as in plasma cleaning and etch processes, and in plasma-enhanced chemical vapor deposition processes. This is especially true where high-energy plasma is present and combined with chemical reactivity to act upon the surface of components present in the environment. It is also an important property when corrosive gases alone are in contact with processing apparatus component surfaces.
Process chambers and component apparatus present within processing chambers which are used in the fabrication of electronic devices and micro-electro-mechanical structures (MEMS) are frequently constructed from aluminum and aluminum alloys. Surfaces of a process chamber and component apparatus present within the chamber are frequently anodized to provide a degree of protection from the corrosive environment. However, the integrity of the anodization layer may be deteriorated by impurities in the aluminum or aluminum alloy, so that corrosion begins to occur early, shortening the life span of the protective coating. Ceramic coatings of various compositions have been used in place of the aluminum oxide layer mentioned above, and have been used over the surface of the anodized layer to improve the protection of the underlying aluminum-based materials. However, the protective layer deteriorates over time and eventually leaves the aluminum alloy subject to attack, even though the life span of the protective layer is extended over that of anodized aluminum.
Yttrium oxide is a ceramic material which has shown considerable promise in the protection of aluminum and aluminum alloy surfaces which are exposed to fluorine-containing plasmas of the kind used in the fabrication of semiconductor devices. In U.S. application Ser. No. 10/075,967 (“the '967 application”), the grandparent application of the present continuation-in part application, which has been allowed, it is disclosed that a yttrium oxide coating applied over an anodized surface of a high purity aluminum alloy process chamber surface or process component surface produces excellent corrosion protection. In particular, the '967 Application pertains to a processing chamber component resistant to a plasma including fluorine and oxygen species. The processing chamber component typically comprises: a high purity aluminum substrate, where particulates formed from mobile impurities have a particle size distribution such that no more than 0.2% of the particles are larger than 20 μm, with no particles being larger than 50 μm; an anodized coating on a surface of the high purity aluminum substrate; and a protective coating comprising yttrium oxide overlying the anodized coating. The protective coating may include aluminum oxide up to about 10% by weight, and typically comprises 99.95% by weight or greater yttrium oxide. The protective coating is coating typically applied using a method such as spray coating, chemical vapor deposition, or physical vapor deposition.
U.S. Pat. No. 5,798,016, to Oehrlein et al., issued Aug. 25, 1998, describes a method and apparatus for etching semiconductor devices where undesirable deposition of films on internal surfaces of the apparatus are prevented using a heatable liner or process chamber wall. The heated liner or chamber wall may be constructed from a “wide variety of materials, for example, ceramics, aluminum, steel, and/or quartz. Aluminum is the preferred material because it is easy to machine.” However, since aluminum is reactive with a number of plasmas, it is recommended that “aluminum oxide or a coating thereof be disposed on the liner or chamber walls”, because aluminum oxide tends to be chemically inert. In addition to the materials used to construct the liner and/or chamber walls, a protective coating may be applied to the surfaces of the liner and/or chamber walls. Examples which are given include Al2O3, Sc2O3, or Y2O3.
U.S. Patent Application Publication No. US 2001/0003271A1, of Otsuki, published Jun. 14, 2001, describes a processing apparatus for semiconductor wafers, where the process may include a plasma, in which a film of Al2O3, or Al2O3 and Y2O3, is formed on an inner wall surface of the chamber and on those exposed surfaces of the members within the chamber which require a high corrosion resistance and insulating property. An example is given of a processing chamber where a base material of the chamber may be a ceramic material (Al2O3, SiO2, AlN, etc.), aluminum, or stainless steel, metal or metal alloy, which has a sprayed film over the base material. The sprayed film may contain an oxide of Y, Sc, La, Ce, Eu, Dy, or the like, or fluoride of one of these metals. The film may be made of a compound of a III-a element of the periodic table, such as Y2O3 The film may substantially comprise Al2O3 and Y2O3. A sprayed film of yttrium-aluminum-garnet (YAG) is also mentioned. The sprayed film thickness is said to range from 50 μm to 300 μm.
U.S. Pat. No. 6,352,611, to Han et al., issued Mar. 5, 2002, describes a dielectric window of a reactor chamber where substrates are processed in a plasma of a processing gas. A ceramic composition of matter used to produce a process kit and a dielectric window preferably contains a ceramic compound (e.g., Al2O3) and an oxide of a Group IIIB metal (e.g., Y2O3). The ceramic compound may be selected from silicon carbide, silicon nitride, boron carbide, boron nitride, aluminum nitride, aluminum oxide, and mixtures thereof; however, aluminum oxide is said to be available in a pure form which does not outgas. The Group IIIB metal may be selected from the group consisting of scandium, yttrium, the cerium subgroup, and the yttrium subgroup; however, yttrium is preferred, with the oxide being yttrium oxide. The preferred process for forming or producing the dielectric member is by thermal processing of a powdered raw mixture comprising the ceramic compound, the oxide of a Group IIIB metal, a suitable additive agent, and a suitable binder agent.
U.S. patent application Ser. No. 10/898,113, filed Jul. 22, 2004, and entitled “Clean, Dense Yttrium Oxide Coating Protecting Semiconductor Apparatus”, which is the parent application of the present continuation-in-part application, discloses a protective coating for a semiconductor processing apparatus component comprising aluminum or an aluminum alloy, where the coating includes a material selected from, for example, but not limited to: yttrium-aluminum-garnet (YAG); an oxide of an element selected from the group consisting of Y, Sc, La, Ce, Eu, and Dy; a fluoride of an element selected from the group consisting of Y, Sc, La, Ce, Eu, and Dy; and combinations thereof. The coating is applied to a substrate surface by thermal/flame spraying, plasma spraying, sputtering, or chemical vapor deposition (CVD). The coating is placed in compression by applying the coating at a substrate surface temperature of at least about 150-200° C. The disclosures of U.S. application Ser. Nos. 10/075,967 and 10/898,113 are hereby incorporated herein by reference in their entirety.
The kinds of protective coatings described above have been used to protect gas distribution plate exposed surfaces for gas distribution assemblies used in semiconductor and MEMS processing apparatus. However, due to the concentration of reactive species which are present at the surface of the gas distribution plate, the lifetime of the gas distribution plate has typically been limited, from about 8 processing days to about 80 processing days. Thus, there is a need in the device and MEMS fabrication industry for a longer lasting gas distribution plate.